SQL Advanced Tutorial

This book is a guide to leveling up your SQL skills, written by MICK, the author of SQL Basic Tutorial and a Japanese database engineer, for readers who want to move from beginner to intermediate level. The book is broadly divided into two parts. Part 1 revisits SQL techniques commonly seen in day-to-day development—CASE expressions, self-joins, the HAVING clause, outer joins, correlated subqueries, the EXISTS predicate, set operations, row-to-row comparison, and working with sequences—and, through numerous sample programs and exercises, explains the easily overlooked uses of these techniques and the logic behind them, helping readers shift gradually from procedural thinking to set-based thinking. Part 2 bridges practice and theory, starting from the history of relational databases and extending to the relational model as seen through set theory and logic, discussing the origin of the name “relational,” the troubles of NULL and three-valued logic, address-type data, hierarchical structures, and other topics, so that readers understand the roots of SQL’s design trade-offs. Most sections end with exercises, and the book closes with answers and references, making it easy for readers to check their own grasp of the material. The book is suited to readers who already have basic SQL knowledge and want to write more concise and efficient queries.